Structural health monitoring comprises a set of techniques to detect defects appearing in structures. One of the most viable techniques is based on the guided ultrasonic wave test (UGWT), which consists of emitting waves throughout the structure, acquiring the emitted waves with various sensors, and processing the waves to detect changes in the structure. The UGWT of layered composite structures is challenging due to the anisotropic wave propagation characteristics of such structures and to the high signal attenuation that the waves experience. Hence, very low amplitude signals that are hard to distinguish from noise are typically recovered. This paper analyzes the propagation of guided waves along a cross-ply composite laminate following an empirical methodology. The research compares several implementations for UGWT with piezoelectric wafer active sensors. The reference for comparison is set on a basic mode, which considers the application of nominal voltage to a single sensor. The attenuation and spreading of the waves in several directions are compared when more energy is applied to the monitored structure. In addition, delayed multiple emission is also considered in multisensor tests. The goal of all the UGWT configurations is to transmit more energy to the structure such that the echoes of the emission are of greater amplitude and they ease the signal processing. The study is focused on the realization of viable monitoring systems for aeronautical composite made structures.

中文翻译：

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跨层复合层压板的超声波导波测试：一项实证研究。

结构健康监测包括一组检测结构中出现的缺陷的技术。最可行的技术之一是基于引导超声波测试（UGWT），该技术包括在整个结构中发射波，使用各种传感器获取发射的波并处理这些波以检测结构中的变化。分层复合结构的UGWT具有挑战性，因为这种结构具有各向异性的波传播特性，并且波经历的信号衰减高。因此，通常会恢复很难与噪声区分开的非常低的幅度信号。根据经验方法，本文分析了导波沿交叉复合层压板的传播。该研究比较了具有压电晶片有源传感器的UGWT的几种实现。用于比较的参考是在基本模式下设置的，该模式考虑将标称电压施加到单个传感器。当更多的能量施加到被监视的结构上时，将比较波在多个方向上的衰减和扩展。另外，在多传感器测试中还考虑了延迟多次发射。所有UGWT配置的目标是向结构传输更多的能量，以使发射的回波具有更大的幅度，并简化信号处理。该研究的重点是实现航空复合材料制成结构的可行监控系统。考虑将标称电压施加到单个传感器上。当更多的能量施加到被监视的结构上时，将比较波在多个方向上的衰减和扩展。另外，在多传感器测试中还考虑了延迟多次发射。所有UGWT配置的目标是向结构传输更多的能量，以使发射的回波具有更大的幅度，并简化信号处理。该研究的重点是实现航空复合材料制成结构的可行监控系统。考虑将标称电压施加到单个传感器上。当更多的能量施加到被监视的结构上时，将比较波在多个方向上的衰减和扩展。另外，在多传感器测试中还考虑了延迟多次发射。所有UGWT配置的目标是向结构传输更多的能量，以使发射的回波具有更大的幅度，并简化信号处理。该研究的重点是实现航空复合材料制成结构的可行监控系统。所有UGWT配置的目标是向结构传输更多的能量，以使发射的回波具有更大的幅度，并简化信号处理。该研究的重点是实现航空复合材料制成结构的可行监控系统。所有UGWT配置的目标是向结构传输更多的能量，以使发射的回波具有更大的幅度，并简化信号处理。该研究的重点是实现航空复合材料制成结构的可行监控系统。